THE EXCRETION OF URINE 



553 



bly because of some change that has occurred in the permeability 

 of its membrane due to inflammation or asphyxia. In these cases the 

 urine is usually reduced in amount. Probably there is no purely glom- 

 erular or tubular type of nephritis, both structures sharing in the dis- 

 ability. When foreign proteins such as egg albumin gain entry to the 

 blood, they appear in the urine. This is also the case when hemoglobin 

 is liberated from the blood corpuscles. In both cases masses of the ex- 

 creted protein in the capsule may be detected by microscopical examina- 

 tion when the kidney is excised and hardened during the excretion. 

 There is also some evidence that the capsule is damaged during the fil- 

 tration of the foreign protein, for it has been found after injecting egg 



Si 



Fig. 173. Nerve supply of the kidney. K, kidney; Si, S 2 , major and minor splanchnic nerves; V, 

 vagus; C.G., Celiac ganglion; A, aorta. (From Cushny.) 



albumin, that more protein may appear in the urine in 24 hours than the 

 amount injected. 



Albuminuria is also readily induced experimentally by clamping the 

 blood vessels of the kidney. After occlusion of the renal artery for 

 30 seconds, the urine for some time ceases entirely to flow, and when 

 it returns (in about an hour) it is loaded with protein which gradually 

 disappears. In all cases of albuminuria the albuminous nitrate in its 

 passage along the tubules is concentrated by the reabsorption process, 

 and this may occur to such an extent that the protein is precipitated 

 so as to form a cast to which detritus from the tubular epithelium may 

 become added, the exact type of cell composing this detritus depending 

 on the point at which the protein solidifies. 



